Variable electrical resistor



y 1959 A. HAYNMAN 2,894,237

VARIABLE ELECTRICAL RESISTOR Filed March 25, 1958 2 Sheets-Sheet 1 28b Fi K in 2s 2 2aa-- O INVENTOR. ALEXANDRE HAYNMAN AMJJJM ATTORNEY y 1959 A. HAYNMAN 2,894,237

VARIABLE ELECTRICAL RESISTOR Filed March 25. 1958 2 Sheets-Sheet 2 INVENTOR. ALEXANDRE HAYNMAN ca /M 66M ATTORNEY United States Patent VARIABLE ELECTRICAL RESISTOR Alexandre Haynman, Copenhagen-Vanlose, Denmark,

assignor to International Resistance Company, Philadelphia, Pa., a corporation of Delaware tApplication March 25, 1958, Serial No. 723,869

12 Claims. (Cl. 338-150) This invention relates to the construction of a rotary type variable resistor and more particularly to a substantially flat, shaftless, rotary type variable resistor.

In the manufacture of electronic equipment it is the present desire to have the electrical components which make up the circuit of the equipment as small as possible, particularly where printed circuit panels are used, so that the components take up as little space as possible in the chassis or on the printed circuit panel. The rotary type variable resistors previously available, although small in diameter, are relatively thick and bulky since they are enclosed in a hollow casing to protect the various parts. Furthermore, such variable resistors are made up of many different and intricate parts which, as the diameter of the resistor is decreased become more intricate and difficult to handle in the assembling of the resistors.

It is therefore an object of this invention to provide a substantially fiat, rotary type variable resistor. It is another object of this invention to provide a substantially flat, shaftless, rotary type variable resistor. It is still another object of this invention to provide a rotary type variable resistor of simple construction which is made up of a minimum number of different parts so as to be easy to assemble and therefore relatively inexpensive. Other objects of the invention will in part be obvious and will in part appear hereinafter.

The invention accordingly comprises the features of construction, combinations of elements and arrangement of parts, which will be exemplified in the constructions hereinafter set forth, and the scope of the invention will be indicated in the claims.

For a fuller understanding of the nature and objects of the invention, reference should be had to the following detailed description taken in connection with the accompanying drawings, in which:

Figure l is a front elevational view of the variable resistor of this invention;

Figure 2 is an exploded perspective view of the variable resistor;

Figure 3 is a front elevational view of a modification of the variable resistor of this invention;

Figure 4 is a cross-sectional view of the modification of the variable resistor taken along line 44 of Figure 3;

Figure 5 is a front elevational view of another modification of the variable resistor of this invention; and

Figure 6 is a front elevational view of a modification of the resistance element used in the variable resistor of this invention.

Referring to the drawing, in which like numerals identify similar parts, Figures 1 and 2 show one modification of the variable resistor which comprises a thin flat mounting plate 10 of an electrical insulating material, such as a plastic, having a circular opening 12 therein. Although mounting plate 10 is shown to be rectangular it can be circular or any other desired shape. A resistance element, generally indicated by 14, rotatably fits in the ice mounting plate opening 12. Resistance element 14 comprises a circular disc 16 of an electrical insulation material having an outer diameter substantially the same as the diameter of mounting plate opening 12 and being of a thickness substantially the same as the thickness of mounting plate 10. Disc 16 has a central aperture 16a with a notch 16b extending radially from aperture 16a and is coated on both of its surfaces with a film of an electrical resistance material, such as carbon or any other well known resistance composition. The resistance material coatings do not extend beyond the end of notch 16b to provide open ended, arcuate electrical resistance paths 18, one on each side of disc 16. Although only the resistance path 18 on one side of disc 16 is shown, the resistance path on the other side of disc 16 is identical to the resistance path shown. Disc 16 is also provided with a hole 20 therethrough at one end of the resistance paths 18. Hole 20 is coated or filled with an electrical conducting material whichmaterial contacts both resistance paths 18 to electrically connect the opposed ends of the two resistance paths. An actuating member 22 of an electrical insulating material fits into disc aperture 16a and has a projection 22a fitting into notch 16b to provide a driving connection with disc 16. Actuating member 22 has a slot 22b therethrough to permit the insertion of a screw driver or some similar tool for rotation of the actuating member. Although disc aperture 16a and actuating member 22 are shown to be circular in shape with a projection and notch driving connection, they may be of any non-circular shape which provides such a connection.

A pair of identical thin, flat cover plates 2424 of electrical insulating material are mounted one on each side of mounting plate 10 to hold resistance element 14 and actuating member 22 in the mounting plate opening 12. Cover plates 24 are of the same size and shape as mounting plate 10 and each of the cover plates 24 has an aperture 26 therethrough of such a size and so located as to expose a portion of the resistance path 18 and the actuating member slot 22b (see Figure 1). A pair of identical conductors 2828 are mounted one on the outer surface of each of the cover plates 24 and adjacent opposite edges of the mounting plate 10. Each of the conductors 28 comprises a strip of an electrical conducting metal having a terminal portion 28a at one end projecting beyond an edge of the cover plates 24 and a curved contact portion 28b, the end of which extends through cover plate aperture 26 and slidably engages resistance path 18. The contact portions 28b of the two conductors 28 engage the resistance paths 18 at directly opposite points on the resistance element 14 for reasons which will be explained later. Each of the conductors 28 is bent intermediate its ends to provide a projection 280 which extends through aligned holes 24a and 10a in the cover plates and mounting plate respectively to align the plates and prevent relative rotation therebetween. Headed rivets 30 extends through aligned holes 28d, 24b and 10b in the conductors, cover plates and mounting plate respectively and the ends of the rivets 30 are peened over to secure the conductors 28 and cover plates 24 to the mounting plate 10.

In use, the resistance of the resistor can be varied by inserting a screw driver or a similar tool into actuating member slot 22b, which is accessible from either side of the resistor, and rotating the actuating member 22 which in turn rotates the resistance element 14. When resistance element 14 is rotated so that hole 20 is directly under the contacts 28b-28b, the resistance across the terminals 28a--28a will be substantially zero since the contacts 28b are electrically connected only through the electrical conducting material in hole 20. As the actuating member 22 is rotated clockwise, as viewed in Figure 1, hole Ztl moves away from contacts 28b and the length of the resistance paths 18 between contacts 28b and hole 20 increases. Thus the resistance across terminals 28a increases until the maximum resistance value is reached when the end of the resistance paths 13 comes under the contacts 28b. The variable resistor can be mounted on a chassis or the like by inserting a mounting pin or bolt through aligned mounting holes 32 and 34 in the cover plates 24 and mounting plate 10 respectively, or on a printed circuit panel by inserting terminals 28a28a through holes in the panel with the resistor supported upright thereon. Thus there is provided a small, flat, shaftless variable resistor of simple construction and composed of a minimum number of different parts so as to be easy and inexpensive to manufacture.

Referring to Figures 3 and 4, there is shown another modification of the variable resistor of this invention which is composed of even a fewer number of different parts. This modification of the variable resistor comprises a mounting plate 40, similar to mounting plate lift of the modification of Figures 1 and 2, having a circular opening 42, therein. A resistance element 44 rotatably fits in the mounting plate opening 42. Referring to Figures 4 and 6, the resistance element 44 comprises a circular disc 46 of an electrical insulation material having a radially extending slot 46a extending from the periphery thereof to a point short of the center of the disc. Both surfaces of disc 46 are entirely coated with a layer of an electrical resistance material and a circular groove 48 is cut through each of the resistance material layers. Grooves 48 are of the same diameter and of a diameter large enough to cross slot 46a to provide an open ended arcuate resistance path 50 on each side of disc 46. Disc 46 also has a central actuating slot 52 and a hole 54 located adjacent one end of the resistance path 50. Hole 54 is filled or coated with an electrical conducting material which electrically connects the resistance paths St) or the opposite sides of disc 46. Identical cover plates 5656, similar to cover plates 24 of the modification of Figures 1 and 2, are mounted one on each side of mounting plate 40. Each of the cover plates 56 has an aperture 58 therethrough which exposes a portion of the resistance paths 50 and the resistance element actuating slot 52. A pair of identical conductors 60-6tl are mounted one on the outer surface of each of the cover plates 56 and adjacent opposite edges of mounting plate 40. Each of conductors of), similarly to the conductors 28 shown in the modification of Figures 1 and 2, comprises a strip of electrical conducting metal having a terminal portion 60a at one end projecting beyond an edge of the cover plates 56 and a contact portion 6%, the end of which extends through cover plate aperture 58 and slidably engages resistance path 50. Each of conductors 60 also has a pair of lugs 62 and 64- punched out of the body thereof. Lugs 62 and 64 respectively extend through aligned holes 56a, 56b and 40a, 40b in the cover plates 56 and mounting plate 40 respectively and the ends thereof are bent over the outer surface of the cover plate opposite to that on which the conductor 60 is mounted to secure the conductors 60 and cover plates 56 to the mounting plate 40.

The modification of the variable resistor shown in Figure is similar to the modification shown in Figures 3 and 4 except that the conductors 66 each have a pair of lugs 68 and 79 which extend from opposite sides of the conductor and are longitudinally spaced apart along the conductor. Lugs 68 and 70 extend through aligned holes in the cover plates and mounting plate and the ends thereof are bent over the outer surface of the cover plate opposite to that on which the respective conductor is mounted to secure the conductors and cover plates to the mounting plate.

The modifications of the variable resistor shown in Figures 3, 4 and 5 operate in the same manner as previously described with regard to the modification of Figures 1 and 2. However, the modifications of the variable resistor of Figures 3, 4 and 5 have the advantage that they are made up of a fewer number of different parts since the resistance element has the actuating member integral therewith and the conductors have the securing members integral therewith. Although the one piece resistance element and actuating member of Figure 6 was described in connection with the modifications of the variable resistor of Figures 3, 4 and 5, it can also be used in the modification of Figures 1 and 2 to replace the two piece resistance element and actuating member assembly.

It will thus be seen that the objects set forth above, among those made apparent from the preceding description, are efficiently attained and, since certain changes may be made in the above constructions without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

It is also to be understood that the following claims are intended to cover all of the generic and specific features of the invention herein described, and all statements of the scope of the invention which, as a matter of language, might be said to fall therebetween.

Having described my invention, what I claim as new and desire to secure by Letters Patent is:

1. A variable electrical resistor comprising the combination of a plate of electrical insulating material having a circular opening therethrough, a circular disc of electrical insulating material rotatably fitting in the opening in said plate, opposed arcuate paths of electrical resistance material on opposite surfaces of said disc, means electrically connecting said resistance paths, means on each side of said plate holding said disc in the opening, a contact of electrical conducting material mounted on each side of said plate, each of said contacts slidably engaging one of said resistance paths and a terminal connected to each of said contacts.

2. The combination as set forth in claim 1 in which the means for electrically connecting said resistance paths comprises a hole through said disc adjacent one of the opposed ends of said paths and an electrical conducting material in said hole and contacting said paths.

3. The combination as set forth in claim 2 in which said contacts engage said resistance paths at opposed points on the surfaces of said disc.

4. A variable electrical resistor comprising the combination of a mounting plate of electrical insulating material having a circular opening therethrough, a circular disc of electrical insulating material rotatably fitting in the opening in said mounting plate, said disc having an outer diameter substantially the same as the diameter of said opening and being of a thickness substantially the same as the thickness of said mounting plate, opposed arcuate paths of electrical resistance material on the opposite surfaces of said disc, means electrically connecting said resistance paths, a cover plate of electrical insulating material on each side of said mounting plate and extending across said disc, an aperture in each of said cover plates exposing a portion of said resistance paths, a contact of electrical conducting material mounted on each of said cover plates, each of said contacts extending through the aperture in their respective cover plates and slidably engaging the resistance path exposed through said apert-ure, means securing the contacts and cover plates to the mounting plate, and terminals connected to said contacts.

5. The combination as set forth in claim 4 in Which the means for electrically connecting said resistance paths comprises a hole through said disc adjacent one of the opposed ends of said paths and an electrical conducting material in said hole and contacting said paths.

6. The combination as set forth in claim 5 in which said contacts engage said resistance paths at opposed points on the stufaces of said disc.

7. The combination as set forth in claim 4 in which the means for securing the contacts and cover plates to the mounting plate comprises rivets extending through said contacts, cover plates and mounting plate.

8. The combination as set forth in claim 4 in which the means for securing the contacts and cover plates to the mounting plate comprises lugs integral with the contacts and extending therefrom through aligned holes in the cover plate opposite to the cover plate on which the respective contact is mounted.

9. The combination as set forth in claim 4 including means associated with said disc and exposed through the apertures in said cover plates by which said disc can be rotated.

10. A variable electrical resistor comprising the combination of a mounting plate of electrical insulating material having a circular opening therethrough, a circular disc of electrical insulating material rotatably fitting in the opening in said mounting plate, said disc having an outer diameter substantially the same as the diameter of said opening and being of a thickness substantially the same as the thickness of said mounting plate, opposed arcuate paths of electrical resistance material on the opposite surfaces of said disc, means electrically connecting said resistance paths at substantially one of their opposed ends, substantially identical cover plates of electrical insulating material on opposite sides of said mounting plate holding said disc in the mounting plate opening, said cover plates being of substantially the same size and shape as said mounting plate and each of said cover plates having an aperture exposing a portion of said resistance paths, a separate metal conductor mounted on the outer surface of each cover plate, said conductors each having a terminal portion at one end extending beyond an edge of said cover plates and a contact portion extending through the apertures in said cover plates and slidably engaging the resistance paths, and means securing the conductors and cover plates to the mounting plate.

11. The combination as set forth in claim 10 in which said conductors are adjacent opposite edges of said mounting plate and the means for securing said conductors and cover plates to said mounting plate comprises rivets extending through said conductors, cover plates and mounting plate.

12. The combination as set forth in claim 10 in which said conductors are adjacent opposite edges of said mounting plate and the means for securing said conductors and cover plates to said mounting plate comprises lugs integral with said conductor and extending therefrom through aligned holes in the cover plates and mounting plate and bent across the outer surface of the cover plate opposite to the cover plate on which the respective conductor is mounted.

References Cited in the tile of this patent FOREIGN PATENTS 

